Among the various video display systems available in the art, an optical projection system is known to be capable of providing a high quality display in a large scale. In such an optical projection system, light from a lamp is uniformly illuminated onto an array of, e.g., M.times.N, actuated mirrors such that each of the mirrors is coupled with each of the actuators. The actuators may be made of an electrodisplacive material such as a piezoelectric or an electrostrictive material which deforms in response to an electric field applied thereto.
The reflected light beam from each of the mirrors is incident upon an aperture of a baffle. By applying an electrical signal to each of the actuators, the relative position of each of the mirrors to the incident light beam is altered, thereby causing a deviation in the optical path of the reflected beam from each of the mirrors. As the optical path of each of the reflected beams is varied, the amount of light reflected from each of the mirrors which passes through the aperture is changed, thereby modulating the intensity of the beam. The modulated beams through the aperture are transmitted onto a projection screen via an appropriate optical device such as a projection lens, to thereby display an image thereon.
In FIGS. 1A to 1F, there is illustrated a method for manufacturing an array 100 of M.times.N electrodisplacive actuated mirrors 50 for use in an optical projection system, disclosed in a copending, commonly owned application, U.S. Ser. No.08/278,472, entitled "ELECTRODISPLACIVE ACTUATED MIRROR ARRAY", the method comprising the steps of: (1) preparing a ceramic wafer 10, made of an electrodisplacive material, having a top and a bottom surfaces 1, 2; (2) forming an array 3 of M.times.N first electrodes 4 on the bottom surface 2 of the ceramic wafer 10; (3) covering the top surface 1 of the ceramic wafer 10 with a conductive metallic layer 5; (4) forming a photoresistive layer 6 on top of the metallic layer 5; (5) providing M vertically directional trenches 7 on the top surface 1 of the ceramic wafer 10 treated in accordance with the steps (2) to (4) using, for example, an etching process, each of the M trenches having a width of 50-70 .mu.m and a depth of 50-100 .mu.m; (6) forming on the top surface 1 of the ceramic wafer 10 treated in accordance with the steps (2) to (5) N-1 horizontally directional grooves thereon (not shown) using an etching process, thereby forming an array 17 of M.times.N electrodisplacive actuators 18; (7) removing the photoresistive layer 6; (8) mounting the ceramic wafer 10 treated in accordance with the steps (2) to (6) on an active matrix 8, comprising a substrate 9 and an array of M.times.N transistors (not shown); (9) placing an array of 11 M.times.N hinges 12 on the ceramic wafer 10 treated in accordance with the above-described steps, wherein each of the M.times.N hinges 12 is provided with a protrusion 15 for its fitting to each corresponding one of the M trenches 7; (10) forming a mirror 19 on the flat top surface 13 of each of the M.times.N hinges 12; and (11) making electrical connections to thereby form an array 100 of M.times.N electrodisplacive actuated mirrors 50.
Major drawback of the above-described method for manufacturing an array of M.times.N electrodisplacive actuated mirrors is that it involves a number of time consuming, hard to control, and tedious processes. One of such processes is the formation of the M vertically directional trenches, each having, as stated above, a width of 50-70 .mu.m and a depth of 50-100 .mu.m, respectively, and formed conventionally by utilizing an etching process or combinations thereof. It is, however, extremely difficult and also time consuming to form the M trenches precisely on the electrodisplacive material using such a procedure.